At present, touch drive lines and touch sensing lines are added into an existing thin film transistor (TFT) array substrate to form a mutual capacitive in-cell touch screen to achieve a touch function. For example, a metal wire matrix is formed along the horizontal direction and the vertical direction of the TFT array substrate; the metal wires in the horizontal direction server as touch drive electrodes, and the metal wires in the vertical direction server as touch sensing electrodes insulated from the touch drive electrodes. The in-cell touch screen operates in such a process: touch drive signals are applied to the touch drive electrodes and voltage signals, over the touch sensing line, coupled out through mutual capacitors are detected. In the process, where a human touches the touch screen, an electric field by his/her body acts on the capacitors formed between the touch sensing electrodes and the touch drive electrodes, so that the capacitance of the capacitors is changed and thereby the voltage signals of the touch sensing line coupled out are changed and the contact location can be determined based on the change of the voltage signals.